Variable focal length optical system for photocopying machine

ABSTRACT

A variable magnification optical system for a photocopying machine wherein a variable lens interposed between an original holder and a copy paper holder spaced apart from the original holder by a predetermined distance varies its focal length within its lens barrel and displaces itself along an optical path passing through a side edge of the original, whereby an image may be magnified or reduced in size with one side edge of a copy paper being a reference line for magnification or reduction.

United States Patent 1 1 3,711,199 Koizumi 1 Jan. 16, 1973 [54] VARIABLEFOCAL LENGTH OPTICAL 56] References Cited PHOTOCOPYING UNITED STATESPATENTS 2,160,277 5/1939 Neidich ..95/4'.5 [75] Inventor Yutaka Japan2,356,620 8/1944 Schade ..95 4.55 [73] Assignee; Kabushiki Kaisha Ricoh,Tok 3,076,392 2/1963 Cerasani ..355/1l Japan 3,437,410 4/1969 Tregayetal... .......355/57 3,539,258 11/1970 Miles ..355/66 [22] Filed: Jan.21, 1972 1 APPL No; 219,885 Primary Examiner'Samuel S. MatthewsAssistant Examiner-Richard M. Sheer Related U.S. Application DataAtt0rney-Erwin Koppel et al. [63] Continuation of Ser. No. 14,288, Feb.26, 1970,

abandon [57] ABSTRACT A variable magnification optical system for aphotoco- [3 l 9 8 Apphcatlon Priority Data pying machine wherein avariable lens interposed Feb. 28, 1969 Japan ....'.44 1s57s between lOriginal hldef and a P P P holder spaced apart from the original holderby a predeter- 52 U.S.Cl. .355/57, 355/60, 355/66 mined distance variesits focal length within its lens 51 Int. Cl. ..G03b 27/34 barrel anddisplaces itself along an Optical p 58 Field ofSearcli ..355 11, 44,45,55, 57, 60, Passing through a Side edge of the Original. whereby 3553 9 ;'9'5 4 5' an image may be magnified or reduced in size with oneside edge of a copy paper being a reference line for magnification orreduction.

1 Claim, 5 Drawing Figures VARIABLE FOCAL LENGTH OPTICAL SYSTEM FORPHOTOCOPYING MACHINE This is a continuation of application Ser. No.14,288 filed Feb. 26, 1970.

BACKGROUND OF THE INVENTION optical system for a photocopying machine.

When the ratio of a distance from a photo lens to a subject to adistance from the photo lens to a sensitized film is considerably largeas in the case of ordinary photography, an image may be varied in sizeonly by displacing a lens within its lens barrel. In a photocopyingmachine since, a distance from an original to a copy paper is relativelyshorter and the magnification power is almost unity, two or more partsof the projection lens must be displaced relative to each other withinits lens barrel (the whole lens system) which in turn must be displacedfor magnification or reduction in size of a projected image. When thelens is'displaced along one optical axis or specifically selected lightray, an image projected upon a copy paper is enlarged or reduced arounda point upon the copy paper. This means that four side edges of aprojected image vary theirpositions as the size of the image is varied.This is one distinct disadvantage for a photocopying machine in which acopy paper is positioned for exposure with its one edge being alignedwith a reference line.

SUMMARY or THE INVENTION One of'the objects of the present invention istherefore to provide a variable magnification optical system for aphotocopying machine in which a projection lens is displaced in thedirection of a specifically selected light ray incident upon a referencepoint upon one side edge of a copy paper so that an image projected uponthe copy paper may beenlarged or reduced in size with said one side edgebeing a reference line.

Another object of the present invention is to provide avariablemagnification optical system best suited for a photocopying machine. I

A further object of the present invention is to provide a variablemagnification optical system simple in construction, compact in size,reliable in operation and inexpensive to manufacture.

In brief, a projection lens of the optical system in accordance with thepresent invention is displaced along a specifically -selected light ray,for example, emanating from one side edge of an original and beingincident upon a preselected line upon a copy paper holder with which isaligned one side edge of a copy paper for exposure. Consequently,irrespective of the position of the projection lens, one side edge of anenlarged or reduced image is always made incoincidence with thepreselected line upon the copy holder, thereby facilitating thepositioning of the copy papers for exposure in a photocopying machine.

The above and other objects, features and advantages of the presentinvention may become more apparent from the following description of oneillustrative embodiment thereof taken in conjunction with theaccompanying drawing.

2 BRIEF DESCRIPTION or THE DRAWING FIG. 1A and B are diagrammatic viewsfor explanation of a variable magnification optical system for aphotocopying machine;

FIG. 2A and B are for explanation of a variable magnification opticalsystem for a photocopying machine in accordance with the presentinvention; and

FIG. 3 is a schematic sectional view of a photocopying machine to whichis applied the optical system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1A and FIG. 2A, on oneside of a variable focus length lens 1 is placed an original 2 to becopied while a sensitized paper or copying paper 3 is placed on theother side of the lens 1. When the focal length of the lens 1 is variedwhile the distance between the original 2 and the copying paper 3remains constant, the magnification of the image projected upon thecopying paper 3 may be varied.

In the optical system shown in FIG. 1A, the variable focus length lens 1is so arranged as to be displaced from the unit reproduction or 1 l (1X) position to an enlargement or reduction position la designated by thedotted line in FIG. 1A, along its optical axis O. When the lens 1 isdisplaced along the optical axis 0 as described above, an image 4reduced in size is obtained around a reference point Os at which theoptical axis 0 intersects with the copying paper 3 at a right angle. Ina photocopying machine, however, there arises one distinct disadvantagewhen an image is reduced symmetrically around the reference point atwhich the stationary optical axis intersects with the photocopyingpaper, thatis the center of a copying paper holder, in view of thepositioning of a copying paper upon the holder and of an original uponan original holder.

In view of the above, in the optical system shown in FIG. 2A, the lens 1is displaced along an optical path A passing one end 2a of the original2 so that as shown in FIG. 2B an image 4 may be reduced in size with theline s-s being a reference line. It is therefore readily understood thatwhen one side edge-of a copying paper is aligned with the stationaryreference line irrespective of a size desired, the handling andpositioning of both an original and a copying paper are much facilitatedin operation, especially when a copying paper is advanced to an exposuresection of a copying machine by means of a conveyor belt, a plurality ofrollers or the like so that it is desired to automatically stop and helda copying paper at a predetermined position for exposure. The abovedescribed arrangement brings about much advantages in practice.

FIG. 3 shows one example of an exposure section of a photocopyingmachine embodying the present invenbetween an original holder 12 and avariable focus length lens 11. The original holder 12 is made of atransparent material. A copy paper 13 isfirmly placed upon a suctionbelt 15 for transporting the copy papers wrapped around a vacuum box 16.

The lensbarrel 17 of the lens 11 is carried by a guide rod (not shown)which is disposed in parallel with optical path A so that the lens 11may be displaced along the optical path A when an image projected uponthe r the image projected upon the copy paper 13 is reduced in size. Itshould be noted, however, that both the point a upon the conveyor belt15 and the point 12aupon the original holder 12 at which the opticalpath A intersects with the belt 15 and the original holder 12respectively remains unchanged so that these points and 15a may beadvantageously used as reference points for positioning the copy papersand originals respectively. Thus, for example when the copy paper whichis being advanced upon the belt 15 in the direction indicated by thearrow may be stopped when the leading edge of the copy paper 13 reachesthe reference point 150, the conveyor belt 15 is stopped for exposure ofthe copy paper 13. Irrespective of the magnification or reduction size,the leading edges of the copy papers may be stopped at the same positionfor exposure so that'an automatic conveyor belt stopping device of theprior art 7 may beus'ed.

In order to. obtain an image enlarged in size, the lens 1-1 maybedisplaced along theoptical path A in the direction toward the reflectingmirror 14, that is the direction opposite to the point 11a. In FIG. 3both of the optical path A and the reflecting mirror 14 are shown asbeing inclined downwardly-relative to the optical axis O, so that thedisplacement of the lens barrel ,17 is much facilitated. Moreparticularly, the distance over which is displaced the peripheral sideedge 17a of thelensbarrel 17 until the latter'contactswith thereflecting mirror 14 can be made longer than that of the case in whichthe lens barrel is displaced alongthe optical axis 0. ln otherwords, aphotocopying machine can be made more compact in size because thedistance between the reflecting mirror and the outermost positionof thelens barrel may be reduced. There exists only a small deviation betweenthe light ray 3- connecting the reference point l2a and the' edge ofthe'len's which is displaced to a magnification or reduction positionand the light ray Ba when the lens 11 is placed at the 11a position, sothat the reflecting mirror maybe smaller in size than. one used in aphotocopying machine in which a'lens barrel is displaced alongtheretracted; and 19, a shield for preventing the light emanated from alight source (not shown) from directly reaching the sensitized surfaceof a copy paper without passing through the projection system.

What is claimed is: 1. A variable magnification optical systemhaving anoptical axis for use in a photocopying machine comprising 1 I anoriginal holder having a first reference line fixedly positioned in saidmachine anda'dapted to have an original placed thereon;

a copy holder having a second reference line fixedly I positioned insaid machine and adapted to have a copy paper positioned thereon,saidcopy holder spaced a fixed distance along said optical axis fromsaid original holder and located substantially at right an les with resect thereto; a mirror ixed in post original holder and said copy holder,said mirror mounted to be inclined with respect to said original holderand said copy holder to provide image reflection I therebetween; avariable focus lens movably mounted between said original holder andsaid copy'holder to focus the light rays for variable magnification;said original having an edge that is positioned and I maintained on saidfirst reference line on said foriginal holder and providing an imagethat is directed along-an optical path reflectable through said mirrorand said variable focus lens'to an edge on said copy paper that ispositioned and maintained on said second reference line on said copyholder',' a

' said variable focus lens being movable to a first position on saidoptical axis to provide a 1:1 magnification of the image of theedge ofsaid original directed along said optical path on said copy paper edge;and 1 said variable focus inclined to said optical axis from said firstposition to a second position, said inclined path corresponding to aline passing through the first and second reference lines whereby theimage of the edge of said original directed along said optical path ismaintained on said second reference line of said copy holder andmagnification of the image of the edge of said original is variable fromsaid lzl magnificatiom i s a I ion and located between said by lightrays passing,

lens being rnovable along a path-

1. A variable magnification optical system having an optical axis for use in a photocopying machine comprising an original holder having a first reference line fixedly positioned in said machine and adapted to have an original placed thereon; a copy holder having a second reference line fixedly positioned in said machine and adapted to have a copy paper positioned thereon, said copy holder spaced a fixed distance along said optical axis from said original holder and located substantially at right angles with respect thereto; a mirror fixed in position and located between said original holder and said copy holder, said mirror mounted to be inclined with respect to said original holder and said copy holder to provide image reflection by light rays passing therebetween; a variable focus lens movably mounted between said original holder and said copy holder to focus the light rays for variable magnification; said original having an edge that is positioned and maintained on said first reference line on said original holder and providing an image that is directed along an optical path reflectable through said mirror and said variable focus lens to an edge on said copy paper that is positioned and maintained on said second reference line on said copy holder; said variable focus lens being movable to a first position on said optical axis to provide a 1:1 magnification of the image of the edge of said original directed along said optical path on said copy paper edge; and said variable focus lens being movable along a path inclined to said optical axis from said first position to a second position, said inclined path corresponding to a line passing through the first and seCond reference lines whereby the image of the edge of said original directed along said optical path is maintained on said second reference line of said copy holder and magnification of the image of the edge of said original is variable from said 1:1 magnification. 